Summary

Stressed, fractured rocks can have complex symmetry. Understanding the compaction and burial history of a basin can be used to better build complex models based on geological concepts and numerical modeling. In this example, we show how 3D stress modeling through basin evolution in time (4D geomechanical basin modeling) enables us to identify fracture orientation based on failure criteria and direction of minimum principal stresses which together with the structural geometry and rock physics modeling can be transformed into the anisotropic elastic stiffness tensor and its symmetry. We demonstrate this integrated concept on a Gulf of Mexico basin model.

Introduction

Modern seismic imaging uses tilted transverse anisotropy (TTI) and tilted orthorhombic (TOR) models to properly image and position. However, building a low-symmetry anisotropic model is a complex process as many rock parameters are needed to describe the subsurface. The relations between geomechanics stress and seismic velocity and anisotropy have been used in the past to predict seismic velocities (Bachrach and Sengupta, 2008; Rodrigues et al., 2014). Direct correlation between stress, fractures, and anisotropy (Thanoon et al., 2015; Mathewson et al., 2015) have been recently observed. However, the elastic properties of the basin are not related only to present day stress and fractures, but also to the history of the basin and the stress path experienced by the sediments. A new research area named as geophysical basin modeling (GBM) has been used to show relations between geohistory and rock properties. This research area have been branching from traditional rock physics and we believe will play a major role in using rock physics relations within their proper geological context. In this paper we present the use of geophysical basin modeling with rock physics to analyze the expected present day anisotropy and symmetry.

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